Recirculating exhaust gases back to the intake manifold of an internal combustion engine lowers combustion temperature and reduces the emission of nitrous oxides into the atmosphere. Exhaust gas recirculation (EGR) valves have been used to regulate the proportion of combustion by-products routed back to the intake manifold.
In the prior art, the amount of gas recirculation was controlled in part by means of a vacuum signal that regulated the opening and closing of the EGR valve. Vacuum ports in a throttle valve housing were used to obtain a pressure indication to control opening and closing of the EGR valve. As the engine throttle is first opened, the vacuum ports couple vacuum to the EGR valve, opening the EGR valve and routing combustibles back to the intake manifold. As the throttle valve opens wider, the vacuum supplied to the EGR valve diminishes and the EGR valve closes. When the engine temperature is below a set point temperature, the EGR valve was closed to prevent rough idling of the engine. Adjusting EGR valve setting based on temperature requires a temperature sensor and a means to control the EGR setting based on the sensed temperature.
U.S. Pat. No. 4,662,604 to Cook discloses an EGR valve for an internal combustion engine. A valve housing supports a valve stem that moves back and forth to open and close the EGR valve in response to energization of a solenoid. The present invention concerns an improved electronically actuated EGR valve wherein exhaust gas flow through the valve is adjusted based upon sensed conditions and a control signal is generated based upon those sensed conditions to adjust the valve setting. The valve includes a solenoid assembly that converts the control signal into a linear movement of a flow-regulating member within the valve.